Scientists found that SARS-CoV-2, the virus that causes COVID-19, can be detected in aerosols for up to three hours and on plastic and stainless steel surfaces for up to three days.

The findings emphasize the importance of hand washing and disinfecting frequently touched surfaces to protect against infection.

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Viruses can live for a time on surfaces outside the human body. According to the CDC, it may be possible to contract the virus responsible for the current outbreak, SARS-CoV-2, by touching a surface or object with the virus on it and then touching your face. However, SARS-CoV-2 is believed to mostly spread from person-to-person through respiratory droplets produced when an infected person coughs or sneezes.

Researchers led by Dr. Vincent Munster of NIH’s National Institute of Allergy and Infectious Diseases (NIAID) studied how long the virus survives in the air and on surfaces. They mimicked how viruses are spread by an infected person onto everyday surfaces in a household or hospital setting, through coughing or touching objects. The team then investigated how long the virus remained infectious on these surfaces.

They compared the results to that of the closely related SARS-CoV-1, which was responsible for the outbreak of Severe Acute Respiratory Syndrome (SARS) in 2002-2004. The findings were published on March 17, 2020, in the New England Journal of Medicine.

The scientists tested the viruses on plastic, stainless steel, copper, and cardboard. They also used a rotating drum to suspend the virus in aerosols, a mist of tiny droplets. This technique was used to determine if the virus could linger in the air.

SARS-CoV-2 remained active on plastic and stainless steel surfaces for two to three days under the conditions in this experiment. It remained infectious for up to 24 hours on cardboard and four hours on copper. The virus was detectable in aerosols for up to three hours. These times will vary under real-world conditions, depending on factors including temperature, humidity, ventilation, and the amount of virus deposited.

The results suggest that people may acquire SARS-CoV-2 through the air and after touching contaminated objects. However, although the viruses were able to infect cells in the laboratory, how much virus is likely to cause infections in people remains to be studied.

As the stability of SARS-CoV-2 seems similar to that of the earlier SARS virus, it’s not clear why COVID-19 has led to a much larger outbreak. During the SARS epidemic, about 8,000 people in 26 countries were infected. That outbreak was contained by isolating people with SARS and identifying those with possible exposure.

“These findings show that SARS-CoV-2 is actually quite similar to SARS-CoV-1 in terms of stability in the environment,” says co-author Dr. James Lloyd-Smith at the University of California, Los Angeles. “This means we can learn from our experiences with SARS in 2002-2004 to gain insights into infection control, especially in healthcare settings. On the other hand, it indicates that the major differences in the epidemiology of these viruses probably arise from other factors—especially the ability of SARS-CoV-2 to be transmitted by people not exhibiting clear symptoms.”

“These results will inform future epidemiologic investigations that will be necessary to understand spread of this virus person to person,” adds co-author Dr. Susan Gerber of the Centers for Disease Control and Prevention.

The findings underscore the importance of hand washing and disinfecting frequently touched objects and surfaces. This can be done using a regular household cleaning spray or wipe. Try to avoid touching your eyes, nose, and mouth. And to help prevent the spread of coronavirus, avoid close contact with those who are sick and stay home if you are sick yourself.